Method of preparing tetramethylammonium azide

ABSTRACT

Tetramethylammonium azide, N(CH 3 ) 4  N 3 , is prepared by a new process per the present invention. In the prior art, preparation of such azide was by use of shock-sensitive starting materials, i.e. AgN 3  and HN 3 . The method of the present invention provides a new method for making such azide at high purity, at room temperature, without the use of shock-sensitive materials.

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment of anyroyalty thereon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the preparation of tetramethylammonium azide,N(CH₃)₄ N₃, particularly preparing such azide without usingshock-sensitive material.

2. The Prior Art

Although tetramethylammonium azide, has been known since 1918, littleinformation has been reported for this interesting compound. Accordingto the previous reports, the compound was prepared by either thereaction of N(CH₃)₄ I with AgN₃ (1) in either water or anhydrous

    N(CH.sub.3).sub.4 I+AgN.sub.3 →N(CH.sub.3).sub.4 N.sub.3 +AgI(1)

ethanol or the neutralization of N(CH₃)₄ OH with aqueous HN₃ (2). Bothpreparations involve the use of shock-sensitive

    N(CH.sub.3).sub.4 OH+HN.sub.3 →N(CH.sub.3).sub.4 N.sub.3 +H.sub.2 O(2)

starting materials, i.e. AgN₃ and HN₃, and suffer from solubility andpurification problems.

Accordingly, there is a need and market for preparation the above azidethat overcomes the above prior art shortcomings.

There has now been discovered a method for preparation of such azidewhich avoids shock-sensitive starting materials and the high costs andlight sensitivity of employing a silver salt per the above prior artmethod. Further the purity of the resulting azide, N(CH₃)₄ N₃ is high.

SUMMARY OF THE INVENTION

Broadly the present invention provides a method for preparing N(CH₃)₄ N₃comprising, reacting the following: ##STR1##

DESCRIPTION OF PREFERRED EMBODIMENT

The invention will become more apparent from the following detailedspecification given below.

The problems of the previous synthesis of N(CH₃)₄ N₃ were overcome byreacting N(CH₃)₄ F with commercially available (CH₃)₃ SiN₃ at roomtemperature in CH₃ CN solution according to: ##STR2##

The conversion of N(CH₃)₄ F to N(CH₃)₄ N₃ is quantitative, and sinceboth trimethylsilyl compounds are volatile at room temperature, verypure and anhydrous N(CH₃)₄ N₃ can be prepared by use of a slight excessof (CH₃)₃ SiN₃ and removal of the solvent, (CH₃)₃ SiF and unreacted(CH₃)₃ SiN₃ at room temperature. None of the materials used in theimproved process are shock-sensitive and the high cost and lightsensitivity of a silver salt are avoided. Furthermore, prolonged heatingfor H₂ O removal and subsequent extractions with CH₃ CN are notrequired, and the purity of the N(CH₃)₄ N₃ prepared by the new processis excellent. The resulting azide compound is a white, crystallinic,nonsensitive and slightly hygroscopic solid. It has little solubility incold CH₃ CN, moderate solubility in hot CH₃ CN and is slightly solublein alcohol and water.

For further discussion of prior art problems in preparingtetramethylammonium azide as well as of the safe preparation of suchazide per the method of the present invention, see the followingArticle. The Article is published in the Journal of the AmericanChemical Society, 1992, Vol. 114, No. 9, pp. 3411-3414 and is entitled"New Synthesis, Crystal Structure, and Vibrational Spectra ofTetramethylammonium Azide and Reactions of the Fluoride Anion with HN₃and of the Azide Anion with HF" by Karl O. Christe et al., which Articleis incorporated herein by reference. Such Article provides considerabledisclosure relative to the molecular structure of N(CH₃)₄ N₃, itscrystal structure, its vibrational spectra, certain related reactions asindicated by the above title of the Article, other physical propertiesof the above azide and other related data and numerous footnotesthereto, all incorporated herein by reference.

The following example is given in illustration of the method of thepresent invention and should not be construed in limitation thereof.

EXAMPLE I

Synthesis of N(CH₃)₄ N₃. A solution of Si(CH₃)₃ N₃ (29.92 mmol) in 15 mLof CH₃ CN was slowly added in a dry atmosphere to N(CH₃)₄ F (24.10 mmol)dissolved in 29 mL of CH₃ CN. In a mildly exothermic reaction, a whiteprecipitate was formed instantaneously. The mixture was agitated forabout 10 min. and then all volatile material was pumped off at roomtemperature. The white solid residue (2.794 g; weight calculated for24.10 mmol of N(CH₃)₄ N₃ =2.797 g, corresponding to a 99.9% yield) wasidentified by vibrational spectroscopy and a crystal structuredetermination, as N(CH₃)₄ N₃. Its decomposition point was found to be255° C. Further information as to the above properties is given in theabove Article, incorporated herein by reference.

What is claimed is:
 1. A method for preparing N(CH₃)₄ N₃ comprising,reacting the following: ##STR3##
 2. The method of claim 1 employing aslight excess of (CH₃)₃ SiN₃ to precipitate said N(CH₃)₄ N₃ withsubsequent removal of the volatiles, (CH₃)₃ SiF and unreacted (CH₃)₃SiN₃.
 3. The method of claim 2 wherein 29.92 mmol of Si(CH₃)₃ N₃ in 15mL of CH₃ CN are slowly added to 24.10 mmol of N(CH₃)₄ F dissolved in 29mL of CH₃ CN to yield 24.10 mmol of N(CH₃)₄ N₃, with subsequent removalof said volatiles.